Well if you have stress tested your cpu/ram/gpu and the system does not crash then my guess would be the same as yours.
I think that card requires a minimum of 450 watts. I have a 650 watt and my system is stable as a rock.

I do not have a multimeter and will probably not invest in one (I'm going to college soon and will only use a laptop), so the PSU is definitely a factor.

Wudaddy, regardless if the rails pass a test with a multimeter that PSU does not have enough on the 12volt rail. If I'm doing my math correctly the 12volt rail on that PSU is only 16.16amps which I'm assuming is not enough total amperage for a system running a 8800GTS. For example it's advised to have 30amps for total system power when running my 3850.
What kind of stability test did you run on your Opteron 170?

My GPU temps aren't that bad, idle is 73C and load I guess is near 90C? I'll double check later (its like an oven in my room at the moment). I had a feeling it had something to do with my PSU since its only 450W and I've been using it for a year or two now.

That is probably the reason for it mate, those temps are pretty damn high and your GPU is overheating. Take the card out and give it a nice clean etc....

Your PSU shouldn't be a problem, because if it was it would just shut off.

Wudaddy, regardless if the rails pass a test with a multimeter that PSU does not have enough on the 12volt rail. If I'm doing my math correctly the 12volt rail on that PSU is only 16.16amps which I'm assuming is not enough total amperage for a system running a 8800GTS. For example it's advised to have 30amps for total system power when running my 3850.
What kind of stability test did you run on your Opteron 170?

Good luck

It has dual 12v rails at 18amps each, so that should be more than enough for my 8800gts. I lowered the overclocks on my card for now to see if there's still the problem. Thanks everyone for trying to help.

@sweet_3025, I've already stated that I had Orthos tested my CPU/RAM and they are stable.

It has dual 12v rails at 18amps each, so that should be more than enough for my 8800gts.

Wudaddy, I understand that but with power supplies that have multiple rails you cannot just add them up. It's completely different then a PSU with a single 12volt rail. Like I said in my previous post, 16amps is extremely low for total system power when running a high end video card such as your 8800GTS.

Wudaddy, I understand that but with power supplies that have multiple rails you cannot just add them up. It's completely different then a PSU with a single 12volt rail. Like I said in my previous post, 16amps is extremely low for total system power when running a high end video card such as your 8800GTS.

Good luck

Yeah I know you can't add them, but someone calculated for me and the total 12v amps from one rail is 28-30amps if I remember correctly, not 36. I'm fairly sure that I have enough amps, I'm just not sure how stable they are.